foreach 循环数据索引作为键

Question

我一直在尝试以索引为键为每个循环 这种情况下，如果输入用户与索引匹配，我想制定一个逻辑，我将显示所有以索引为键的数据

我这样做了两堂课

class DataContainer
    {

        public DataContainer()
        {

        }


        public int index { get; set; }
        public List<DataValue> DataValue { get; set; }
    }
    class DataValue
    {
        public DataValue()
        {

            IntegerValues = new List<int>();
        }
        public string name { get; set; }
        public List<int> IntegerValues { get; set; }
    }

之后我尝试制作这样的数据容器列表

List<DataContainer> harakatSininilMabsutoh = new List<DataContainer>(){
        new DataContainer{index = 2015 , DataValue = new List<DataValue>()
         {
             new DataValue{name = "first",IntegerValues = {9,55,18,11}},
             new DataValue{name = "second"   ,IntegerValues = {5,54,18,11}},
             new DataValue{name = "third" ,IntegerValues = {40,26,14,11}},
             new DataValue{name = "four"    ,IntegerValues = {22,0,5,10}},
             new DataValue{name = "fifth"    ,IntegerValues = {46,44,17,0}},

         }
         },
          new DataContainer{index = 2013 , DataValue = new List<DataValue>()
         {
             new DataValue{name = "first",IntegerValues = {26,49,8,11}},
             new DataValue{name = "second"   ,IntegerValues = {19,42,8,11}},
             new DataValue{name = "third" ,IntegerValues = {55,3,12,11}},
             new DataValue{name = "fourth"    ,IntegerValues = {27,4,23,8}},
             new DataValue{name = "fifth"    ,IntegerValues = {43,22,7,1}},

         }
         },
          new DataContainer{index = 2001, DataValue = new List<DataValue>()
         {
             new DataValue{name = "first",IntegerValues = {35,44,27,10}},
             new DataValue{name = "second"   ,IntegerValues = {24,41,27,10}},
             new DataValue{name = "third" ,IntegerValues = {36,30,26,10}},
             new DataValue{name = "fourth"    ,IntegerValues = {59,24,8,6}},
             new DataValue{name = "fifth"    ,IntegerValues = {29,27,26,1}},

         }
          }
   };

然后我做了一个这样的逻辑

    int years = (this is user input);
    if(years == 2015)
{
    ///How to for each this which has index 2015
}
else if (years = 2013)
{
         //how to foreach this which has index 2013
}
else if (years = 2001)
{
         //how to foreach this which has index 2001

Answer 1

最简单的就是像这样使用LINQFirstOrDefault

int userinput = 2015;
DataContainer requested = harakatSininilMabsutoh.FirstOrDefault(x => x.index == userinput);
if (requested == null) //FirstOrDefault of a class will return null if not found
    return;
foreach (DataValue val in requested.DataValue) 
    Console.WriteLine(val.name + ": " + string.Join(", ", val.IntegerValues));          

编辑 2：

如果您只需要所有整数，没有名称，没有其他任何东西，那么您可以这样做以获得List<List<int>>：

int userinput = 2015;
List<List<int>> intValuesOnly = harakatSininilMabsutoh
    .FirstOrDefault(x => x.index == userinput)
    .DataValue
    .Select(y => y.IntegerValues)
    .ToList();
//Do whatever you want with intValuesOnly. This is everything that you have in a list of lists

或者这样做得到List<int>（扁平化）：

int userinput = 2015;
List<int> intValuesOnly = harakatSininilMabsutoh
    .FirstOrDefault(x => x.index == userinput)
    .DataValue
    .SelectMany(y => y.IntegerValues)
    .ToList();
//Do whatever you want with intValuesOnly. This is everything that you have in single list

如果userinput 未找到，FirstOrDefault 可能会返回 null，请注意，如果您不使用 C#6，则可能需要考虑两步 LINQ：

int userinput = 2015;
DataContainer requested = harakatSininilMabsutoh.FirstOrDefault(x => x.index == userinput);
if (requested == null) //FirstOrDefault of a class will return null if not found
    return;
List<List<int>> intValuesOnly = requested
    .Select(y => y.IntegerValues)
    .ToList();
//Do whatever you want with intValuesOnly. This is everything that you have in a list of lists

Answer 2

首先，请注意，在这一行中，您尝试使用类型名称作为属性名称：

public List<DataValue> DataValue { get; set; }

我已将此属性重命名为“DataValues”，如下所示：

public List<DataValue> DataValues { get; set; }

您有一个列表 ('harakatSininilMabsutoh')，其中的每个元素都是一个 DataContainer。列表中的每个 DataContainer 都有两个属性：一个索引和一个“DataValues”列表（注意从您帖子中的“DataValue”重命名）。

因此，您想要的循环逻辑将是这样的：

var matchingYears = harakatSininilMabsutoh.Where(h => h.index == years);

foreach (var dataContainer in matchingYears)
{
    foreach (var item in dataContainer.DataValues)
    {
        // Action required on each DataValue:
        Debug.Print(item.name + " " + string.Join(",", item.IntegerValues));
    }
}

您需要在您的类中添加以下“using”语句，因为“Where”是一种 LINQ 扩展方法：

using System.Linq;

如果您知道恰好有一个匹配年份，您可以添加First() 并删除外部foreach 循环。如果您知道最多会有一个匹配年份（但可能为零），您仍然可以删除外部 foreach 循环，但您应该改用 FirstOrDefault() 并测试 null。